[terhardp]

Thank you for your responses and insights.

Yes, I've forgotten about the fact that once you've installed and activated W10 on a certain PC, you should be able to do it again later free of charge, despite going back to an earlier version of the OS for the time being, like in my case. I hope I'm getting this right, as I've already upgraded my other two systems and would like to take the advantage for my DAW too in the future.

The main thing is that switching to PT12 is too costly for me at the moment. I've foolishly missed an opportunity to upgrade before end of 2015. thinking that PT12 won't bring any earth-shattering new features. So now I must pay for a reinstatement (twice the earlier price + VAT). According to Avid, W10 still isn't qualified for Pro Tools even with PT12, and judging from other users posts, there are still problems. So if one need to stick to W7, I might as well stick to PT11 and delay the upgrade to PT12 at some more opportune time.